As substituted phenylethanolaminotetralin derivatives, for example, compounds represented by the general formula: ##STR3## (wherein R.sup.a represents a hydrogen atom or an ethyl group; and Y represents a hydrogen atom or a chlorine atom), the hydrochloride or oxalate thereof, or single optical isomers thereof and a compound represented by the formula: ##STR4## (wherein the carbon atom marked with (R) represents a carbon atom in (R) configuration; and the carbon atom marked with (S) represents a carbon atom in (S) configuration), which have gut selective sympathomimetic and antipollakiuria activities, have been disclosed (cf., published Japanese patent application (kohyo) No. Hei 6-506676 and published Japanese patent application (kohyo) No. Hei 6-506955). However, these compounds are .beta..sub.3 -adrenergic receptor stimulating agents having a remarkable .beta..sub.3 -adrenergic receptor stimulating effect.